Stroke is a common cause of death and disabling neurologic disorder. Approximately 700,000 patients suffer from stroke in the United States every year. Hemorrhagic stroke accounts for 20% of the annual stroke population. Hemorrhagic stroke is due to a rupture of a blood vessel in the brain, causing bleeding into the brain tissue and resulting in a hematoma (a blood mass) in the brain. Prompt removal of the blood mass is necessary to limit or prevent long-term brain injury. Removal of the blood mass requires access through the skull and brain tissue, and this is usually accomplished by inserting a cannula through a small burr hole in the skull (created by a drill), or a larger hole created with a saw (a craniotomy or craniotomy hole), and forcing the cannula through the brain. To minimize trauma to the brain, this is currently accomplished with a cannula and obturator assembly, in a method that entails pushing a fairly large cannula, with an obturator disposed in the lumen of the cannula and protruding distally from the cannula, into the brain, using the tip of the obturator to push aside brain tissue to minimize trauma.
Wilson, Apparatus and Methods for Performing Brain Surgery, WO2006/050047 (Nov. 5, 2006) proposed inserting a small diameter expandable sleeve over a stylet, followed by forcing a larger diameter cannula down into the sleeve. Translation of the rigid cannula down into the sleeve serves to gradually expand the sleeve, from the proximal end (nearest the entry point) to the distal end (nearest the target site) and gently retract the brain. Also, Wilson discloses inserting a tube comprising expandable braid covered in an expandable sleeve, in a small diameter configuration, and pushing on both the proximal and distal ends of the braid to force it expand and foreshorten, to create a large lumen tube in the brain.